1. Field of the Invention
The present invention relates to an ion source and to an ion implanter that includes the ion source. More particularly, the present invention relates to an ion source for generating ions (dopants) that are doped into a surface portion of a semiconductor substrate in processes for fabricating a semiconductor device, and an ion implanter that includes the aforementioned ion source.
2. Description of the Related Art
In general, a semiconductor device is manufactured by a fabrication process for forming an electrical circuit on a silicon wafer that is used for a semiconductor substrate, an electrical die sorting (EDS) process for testing electrical characteristics of the electric circuit, and a package process for enclosing the substrate with an epoxy resin and then separating the substrate into individual single chips.
The fabrication process includes a deposition process for forming a layer on the wafer, a chemical mechanical polishing process for planarizing a surface of the layer, a photolithography process for forming a photoresist pattern on the layer, an etching process for forming a pattern having electrical characteristics using the photoresist pattern as an etching mask, an implantation process for implanting ions into predetermined regions of the wafer, a cleaning process for removing particles from the surface of the wafer, a drying process for drying the wafer after the cleaning process, and a testing process for detecting defects on the layer or the pattern of the clean, dry processed wafer.
The implanting process is preformed to be doped in a predetermined region of the semiconductor substrate with ions by implanting these ions into the predetermined region of the semiconductor substrate. An ion implanter for performing the implanting function includes an ion source for generating the ions. Examples of this ion source are disclosed in U.S. Pat. No. 6,022,258 (issued to Abbott et al.), U.S. Pat. No. 6,184,532 (issued to Dudnikov et al.), and U.S. Laid Open Publication No. 2002-0185607.
The ion source includes an arc chamber for generating the ions therein and a filament for thermoelectrically emitting electrons into the arc chamber. A filament current is applied to the filament so that the filament emits the electrons. An arc voltage biased with respect to the filament current is applied to the arch chamber. That is, the filament is used as a cathode and the arc chamber is used as an anode.
The filament is electrically insulated from the arc chamber with an insulating member. The electrons are thermoelectrically emitted from the filament by applying a filament current to the filament. The emitted electrons collide with molecules in a source gas so that the ions are generated.
During emitting the electrons, the filament may be deteriorated due to thermal stress caused by high temperature. This deterioration is generated at a central portion of the filament from which the electrons are mainly emitted and at a portion of the filament adjacent to the arc chamber. The deterioration of the filament decreases the emission rate of the ion source. If the deteriorated filament is broken, the amount of down time of the ion source and the ion implanter may be increased.